Why You Need to Fix that Exhaust Leak

Why You Need to Fix that Exhaust Leak

An automotive exhaust leak can come on slowly, but once they start they continue to grow in size. Whether it’s a leaking exhaust manifold or rotted out muffler we’ve all seen people driving around trying to ignore the problem. Here we’ll discuss why it makes dollars and sense to take care of the problem sooner rather than later.

Two Types of Exhaust Leaks

Let’s face it, times are tough and we all have better things to spend our money on than car repairs. Often drivers will put exhaust leaks on the back burner of things to fix, because the issue doesn’t stop the car from starting and getting them to work or food shopping. Here we’ll talk about exhaust leaks in front of the catalytic converter and those that occur after the converter. See why they are different and review compelling reasons to fix both types.

Pre Catalyst Exhaust Leaks

Although it’s wise to take care of any leaking exhaust parts immediately the ones that occur in front of the catalytic converter can become costly when ignored. For this reason mechanics consider issues in front of the catalyst as a priority one repair. These leaks occur before the first set of oxygen sensors and therefore can provide inaccurate data to the computer calculating the air fuel ratio. The three primary problems caused in this scenario are poor fuel economy, a check engine light code and high exhaust emissions.

When the exhaust system leaks in front of the converter additional oxygen is mixed in with the exhaust gases providing erroneous oxygen sensor data. Another downside of having too much oxygen in the exhaust stream before it enters the inlet of the catalytic converter is the increased o2 raises temperatures inside the converter. How quickly the component is destroyed depends on the severity of the leak. Nevertheless, this excess heat will eventually damage the honeycomb inside, causing it to break apart. If the debris forms an exhaust restriction an engine hesitation complaint is likely.

Parts that Leak Before the Converter

The exhaust manifold is one of the possible areas for an exhaust leak to occur before the catalytic converter. These parts can leak at the sealing gasket where they attach to the cylinder head. They can also leak where the exhaust manifold outlet attaches to the down pipe leading to the converter. In this area they use a sealing gasket often referred to as an exhaust doughnut.

They make the ring shaped sealing part of composite heat resistant materials that seals the pipe while allowing it to flex as the vehicle travels over bumps. This movement can cause deterioration after long periods of time. Another possible issue, although it’s not as common as leaking exhaust seals, is a cracked exhaust manifold. When this happens the car moves from quiet to loud quickly as it leaks from the damaged area.

Exhaust Leaks after the Catalytic Converter

Many automobiles have four oxygen sensors divided into two banks. They further divide them into before and after the converter, so the power train control module can keep an eye on the efficiency of the catalyst. Exhaust leaks after the last set of O2 sensors will not affect fuel economy or the way the vehicle performs like the pre-converter leaks described above. However, they will drastically change tailpipe emission readings.

In states that perform smog checks or some kind of state emission testing, vehicles with exhaust leaks will fail. Another reason to fix this type of exhaust leak is the automotive manufacturer intended for the exhaust to exit from the rear of the car. Exhaust leaks in the middle of the automobile can expose the occupants to the fumes intended to exit the tailpipe.

Leaking Parts after the Catalyst

Without a doubt the most common exhaust leak in the rear section of pipe is from the muffler. However, many automobiles also have a resonator installed between the muffler and the tailpipe. This component further muffles the sound before it exits the car. Both of these components have the tendency to collect water.

This is because of the temperature differential between the warm parts and the cooler air. A muffler and a resonator both have weep holes allowing the condensation to exit the component. As they age, flakes of rust can block these holes and allow the water to stay inside and rot out the parts.

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